Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, 2601, Australia.
Geological Institute, ETH Zurich, Sonneggstr. 5, 8092, Zurich, Switzerland.
Sci Rep. 2017 Nov 29;7(1):16572. doi: 10.1038/s41598-017-16528-6.
The variability of seawater temperature through time is a critical measure of climate change, yet its reconstruction remains problematic in many regions. Mg/Ca and oxygen isotope (δ O) measurements in foraminiferal carbonate shells can be combined to reconstruct seawater temperature and δ O (δ O). The latter is a measure of changes in local hydrology (e.g., precipitation/evaporation, freshwater inputs) and global ice volume. But diagenetic processes may affect foraminiferal Mg/Ca. This restricts its potential in many places, including the Mediterranean Sea, a strategic region for deciphering global climate and sea-level changes. High alkalinity/salinity conditions especially bias Mg/Ca temperatures in the eastern Mediterranean (eMed). Here we advance the understanding of both western Mediterranean (wMed) and eMed hydrographic variability through the penultimate glacial termination (TII) and last interglacial, by applying the clumped isotope (Δ ) paleothermometer to planktic foraminifera with a novel data-processing approach. Results suggest that North Atlantic cooling during Heinrich stadial 11 (HS11) affected surface-water temperatures much more in the wMed (during winter/spring) than in the eMed (during summer). The method's paired Δ and δ O data also portray δ O. These records reveal a clear HS11 freshwater signal, which attenuated toward the eMed, and also that last interglacial surface warming in the eMed was strongly amplified by water-column stratification during the deposition of the organic-rich (sapropel) interval known as S5.
海水温度随时间的变化是气候变化的一个关键衡量标准，但在许多地区，其重建仍然存在问题。有孔虫碳酸盐壳中的镁/钙和氧同位素（δO）测量可以结合起来重建海水温度和δO（δO）。后者是衡量当地水文变化（如降水/蒸发、淡水输入）和全球冰量变化的指标。但成岩作用过程可能会影响有孔虫的镁/钙。这限制了它在许多地方的应用，包括地中海，这是一个破译全球气候和海平面变化的战略地区。高碱度/盐度条件尤其会使东地中海（eMed）的镁/钙温度产生偏差。在这里，我们通过应用凝聚同位素（Δ）古温度计来研究末次冰消期（TII）和上一个间冰期的西地中海（wMed）和东地中海（eMed）的水文学变异性，通过一种新的数据处理方法来研究浮游有孔虫。结果表明，北大西洋在 Heinrich 冰期 11 期（HS11）的冷却对 wMed 的表层水温影响更大（在冬季/春季），而对 eMed 的影响较小（在夏季）。该方法的成对Δ和δO数据还描绘了δO。这些记录显示了一个明显的 HS11 淡水信号，该信号在向 eMed 方向减弱，并且 eMed 在上一个间冰期的表层变暖在富含有机物质（萨布罗佩尔）间隔 S5 的沉积期间由于水柱分层而得到了强烈放大。
